by Calum MacLeod and Robin Webb, USA TODAY

by Calum MacLeod and Robin Webb, USA TODAY

An underwater robotic submarine is expected to finish searching a narrowed-down area of the Indian Ocean seabed for the missing Malaysia Airlines plane within a week, the agency coordinating the search announced Saturday.

To date, the U.S. Navy's Bluefin-21 sub has scanned 51 square miles of ocean floor. The sub completed its sixth mission overnight Friday and was searching again Saturday in the waters off the coast of western Australia. The latest data are still being analyzed, but nothing of interest has been noted, the Joint Agency Coordination Center (JACC) said in a statement.

Up to 11 aircraft and 12 ships continued the search for Flight 370 on Saturday as the hunt enters its sixth week. The Australian Maritime Safety Authority planned a visual search of a 19,382-square-mile area Saturday, the JACC said. So far, not a single piece of debris has been recovered, and the search area may be expanded after the sub completes the current search area.

Malaysian Defense Minister Hishamuddin Hussein told reporters in Kuala Lumpur that there are no plans to give up once the Bluefin concludes its work. Instead, he said, the scope of the search may be broadened or other assets may be used.

"The search will always continue," he said. "It is just a matter of approach. All efforts will be intensified for the next few days with regards to the underwater search."

Officials hope to find physical evidence that they are searching in the right spot for the Boeing 777, which vanished March 8 with 239 aboard on a flight from Kuala Lumpur, Malaysia, to Beijing.

The Bluefin is searching water 15,000 feet deep. Sound-locating equipment had last picked up sounds consistent with an airplane's black box on April 8, but since then the "pings" have gone silent.

Radar and satellite data show the plane flew far off-course and would have run out of fuel in a remote section of the Indian Ocean.